Studying nucleation aspects and morphology of iron (II) oxalate dihydrate crystals in water and diluted phosphoric acid medium

Abstract

Nucleation fundamentals and morphologies of iron II oxalate dihydrate crystals, FeC2O4 2H2O, in deionized water and diluted phosphoric acid (28% P2O5) media were studied. Oxalic acid and iron II sulfate heptahydrate crystals were mixed with deionized water and diluted phosphoric acid (28% P2O5) media at 25 C with concentration range of 2.7–7.2 g/100 mL. The turbidity of the reaction mixture was measured at different time intervals and the induction time of iron II oxalate dihydrate crystals was calculated. It was found that, the increase of induction time in phosphoric acid medium is more than that in deionized water at the same concentration of iron II oxalate dihydrate crystals. The nucleation rates are 30.5 1028 nuclei/cm3 s and 70.2 1028 nuclei/cm3 s at 7.2% concentration of iron II oxalate dihydrate in deionized water and phosphoric acid media, respectively. The surface energy increases in water medium compared to phosphoric acid medium. In addition, the formed crystals are converted from cubic to rectangular shape with increasing concentration of iron II oxalate dihydrate in water medium. On the other hand, the crystals are converted from cubic to octahedral while changing the medium from water to phosphoric acid at 2.7% iron II oxalate concentration.